LONDON — One of the main suspects in the poisoning of ex-Russian agent Alexander Litvinenko can testify by video link at an inquiry into the death, the judge in charge said Monday.

Judge Robert Owen said he was willing to grant Dmitry Kovtun "core participant" status at the inquiry. He said Kovtun could testify July 27 provided he meets conditions, including submitting a full witness statement.

Litvinenko, a KGB officer-turned-Kremlin critic, died after drinking tea laced with radioactive polonium-210 at a London hotel in 2006.

British police have accused two Russian men — Kovtun and Andrei Lugovoi — of the killing. Both deny involvement, and Russia refuses to extradite them.

Earlier this month Kovtun contacted the inquiry, offering to take part.

Owen criticized his delay, saying "this application could and should have been made months ago."

Kovtun's application will postpone the end of the inquiry. Public hearings had been due to finish this week.

Lugovoi has declined to appear, accusing the inquiry of attempting to "whitewash" the involvement of British intelligence in Litvinenko's death.

On his deathbed, Litvinenko accused Russian President Vladimir Putin of ordering his assassination, and Britain has also alleged that the Russian state was involved.

The killing soured U.K.-Russian relations for years, and the investigation into the death stalled — first because Russia refused to hand over the suspects, then because British authorities would not disclose classified intelligence evidence.

Under the terms of the inquiry, that evidence will be heard in secret, after public hearings end.

Owen said that Kovtun would not be given access to the secret evidence. Some other participants, including Litvinenko's widow Marina and the Metropolitan Police, also have not been allowed to see it.

Marina Litvinenko's lawyer, Ben Emmerson, said he felt discomfort at Kovtun being allowed "effectively to mount the defense he's too cowardly to come and mount in a criminal court."

"But we all recognize that the more open and transparent and inclusive the proceedings are, the harder it will be to attack the inquiry's findings with unfair criticism," he said.